(1). Field of the Invention
The invention is directed to an articulating anti-extrusion support system for use with a well tool including a well plug having an expandable elastomer member.
(2). Brief Description of the Prior Art
During the drilling, completion or workover of a subterranean well, it is frequently necessary to isolate one or more zones or sections of the well for various purposes. A permanent or retrievable well plug, such as a packer, bridge plug, tubing hanger assembly, or the like, will include an elastomer member for sealing across an interior area in casing or other well bore tubular previously set within the well. The elastomer member of such devices is expandable from a retracted position during run-in through the casing or open hole on a conduit member, such as tubing wire line or electric line, and are activated to seal within the well bore or casing through expansion.
The elastomeric member of the well plug may be a series of rubber-like solid seal elements which are squeezed or compressed into sealing engagement with the well casing by a compressive force generated or transmitted through the well tool.
Some such well plugs require up to 16,000 pounds of force directed through the device to impart a compressive stress in the elastomer which causes it to form the necessary hydraulic seal in the well. During the application of such high compressive forces, such elastomers do not remain static, but ooze and squeeze or otherwise result in analastic behavior, often referred to as "creep" and/or stress relaxation. After the compressive force has been applied for considerable time through such elastomer, stress relaxation through the elastomer may occur. Accordingly, well plugs which can maintain high compressive loads during deformation during the setting procedure are highly desirable. The elastomer sections, in turn, require means for resisting compressive load extrusion during the setting procedure to maximize and sustain sealing integrity. Typical of the prior art is U.S. Pat. No. 3,872,925, which teaches an expandable anchoring mechanism which includes expandable fingers for anchoring the device into the casing. A similarly designed anchoring mechanism incorporating a packer element is shown in U.S. Pat. No. 3,706,342. Likewise, U.S. Pat. No. 4,554,973 teaches the use of an elastomer support system which includes a crushable element which expands during setting to define a series of radially extending petals which overlap for support of the elastomer, but no platform or other mechanism is provided for supporting the crushable elements. A similar configuration without a support platform is disclosed in U.S. Pat. No. 5,010,958.
The present invention is directed to the problems associated with such prior art mechanisms.